//===================================================================================
// Microsoft patterns & practices
// Composite Application Guidance for Windows Presentation Foundation and Silverlight
//===================================================================================
// Copyright (c) Microsoft Corporation.  All rights reserved.
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE.
//===================================================================================
// The example companies, organizations, products, domain names,
// e-mail addresses, logos, people, places, and events depicted
// herein are fictitious.  No association with any real company,
// organization, product, domain name, email address, logo, person,
// places, or events is intended or should be inferred.
//===================================================================================
using System;
using System.Collections.Generic;

namespace Microsoft.Practices.Prism.Events
{
	/// <summary>
	/// Implements <see cref="IEventAggregator"/>.
	/// </summary>
	public class EventAggregator : IEventAggregator
	{
		private readonly Dictionary<Type, EventBase> events = new Dictionary<Type, EventBase>();

		/// <summary>
		/// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance.
		/// </summary>
		/// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam>
		/// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns>
		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1004:GenericMethodsShouldProvideTypeParameter")]
		public TEventType GetEvent<TEventType>() where TEventType : EventBase, new()
		{
			EventBase existingEvent = null;

			if (!this.events.TryGetValue(typeof(TEventType), out existingEvent))
			{
				TEventType newEvent = new TEventType();
				this.events[typeof(TEventType)] = newEvent;

				return newEvent;
			}
			else
			{
				return (TEventType)existingEvent;
			}
		}
	}
}